Secondly, we may notice that, from the state of physical science at the period when Van Helmont, Paracelsus, and others began to penetrate into its recesses, it was an unknown, obscure, and ill-defined region, and did not permit those who laboured in it to give that precise and accurate account of their discoveries which the progress of reasoning experimentally and from analysis has enabled the late discoverers to do with success. Natural magic--a phrase used to express those phenomena which could be produced by a knowledge of the properties of matter--had so much in it that was apparently uncombined and uncertain, that the art of chemistry was accounted mystical, and an opinion prevailed that the results now known to be the consequence of laws of matter, could not be traced through their various combinations even by those who knew the effects themselves. Physical science, in a word, was cumbered by a number of fanciful and incorrect opinions, chiefly of a mystical character. If, for instance, it was observed that a flag and a fern never grew near each other, the circumstance was imputed to some antipathy between these vegetables; nor was it for some time resolved by the natural rule, that the flag has its nourishment in marshy ground, whereas the fern loves a deep dryish soil. The attributes of the divining-rod were fully credited; the discovery of the philosopher's stone was daily hoped for; and electricity, magnetism, and other remarkable and misconceived phenomena were appealed to as proof of the reasonableness of their expectations. Until such phenomena were traced to their sources, imaginary and often mystical causes were assigned to them, for the same reason that, in the wilds of a partially discovered country, according to the satirist, "Geographers on pathless downs Place elephants for want of towns."